International Publication No. 2014/045847 discloses a touch panel which can detect a touch position on a screen and a pressing amount with respect to the screen. The touch panel disclosed in the foregoing document includes a dielectric film, a piezoelectric body film, and electrodes which sandwich each film. One principal surface of the dielectric film is an operation surface and when a user approaches and/or touches this operation surface, the electrodes sandwiching the dielectric film detect a change in a capacitance and detect a touch position based on a change in this capacitance. Furthermore, when the operation surface is pressed, electrodes sandwiching the piezoelectric body film detect a piezoelectric voltage thereby indicative of a pressing amount.
In order to detect a touch position, a capacitive touch panel needs to apply detection signals to electrodes, measure a response of the electrodes, stop applying the detection signals until next measurement is started, and discharge charges accumulated in the electrodes. When both a piezoelectric voltage and a pressing amount are detected while the charges are being discharged, the piezoelectric voltage sometimes changes and it is not possible to precisely detect the pressing amount.
It is therefore an object of the present invention to provide a touch input device and a touch input detecting method which can detect a pressing amount without being influenced by touch position detection processing.